1. Field of the Invention
The present invention relates generally to a variable lamination manufacturing (VLM) process and apparatus, and more particularly to a variable lamination manufacturing (VLM) process and apparatus, which is capable of fabricating a three-dimensional product by cutting strip-shaped material, such as foamed resin, thermoplastic resin, thermosetting resin, etc., into the unit shape part of variable width, inclinations and length using a four-degree-of-freedom linear heat cutting device, and stacking and bonding together the cut unit shape parts while the material is supplied in variable widths and thicknesses.
In addition, the present invention relates to a rapid prototyping method that is capable of obviating the need for post-processing and considerably reducing build time by improving the dimensional accuracy of the product in comparison with conventional rapid prototyping methods for fabricating trial products and molds.
2. Description of the Prior Art
A rapid prototyping method in accordance with the present invention can be utilized in various industrial uses, such as the fabrication of architectural models, trial products (of the turbine blades of aircrafts, of the impeller of centrifugal compressors, of cellular phones, or of the like), character products (such as Pikachu dolls, Dooly dolls, or the like), cores for lost foam casting, or the like. In particular, the rapid prototyping method can be utilized in the rapid production of parts each having three-dimensional shape that cannot be fabricated by a three or five-axial cutting process.
The conventional rapid prototyping methods may be classified into a method of hardening liquid material into a three-dimensional shape by the irradiation of laser beams and a method of bonding solid material in the form of particles or laminates into a product of a desired shape.
In the above description, the rapid prototyping method denotes a fabricating method of fabricating nonmetallic or metallic material, such as paper, wax, ABS or plastic, directly into a trial product or mold of a three-dimensional shape using three-dimensional computer aided design data. Recently, various materials such as metallic powder and metallic wire have been developed to be utilized as material for rapid prototyping methods.
In the meantime, stereolithography, one of the hardening methods, developed by 3D System Company is a method wherein a liquid photopolymer is selectively irradiated by laser beams to be solidified and one polymer layer is stacked on top of another.
As the stereolithography, there are known a method of partially irradiating laser beams commercialized by 3D System Co., Quadrax Co., Sony Co. and Dupont Co. and a method of irradiating a layer at a time using an ultraviolet lamp commercialized by Cubital Co. and Sculpting Co.
However, the stereolithography has a shortcoming in that solidified photopolymer contracts during hardening, thus being deformed. In addition, when a product having a protrusion is fabricated, there occurs a shortcoming that a support is needed to support photopolymer used to form the protrusion and prevents it from falling down. Furthermore, resin should be employed for the stereolithography, so that the strength of a product is reduced, thereby preventing the product from being functionally utilized.
As the method using powdered material, there are known selective laser sintering commercialized by DTM Co. and three dimension printing commercialized by Solingen Co., Z Corp., etc. and developed by MIT.
In the selective laser sintering, a product is fabricated in such a way that powdered plastic material is spread and the powder material is boned together by the irradiation of laser beams. The selective laser sintering is used to fabricate a metallic product and a mold using iron powder coated with plastic.
When a metallic product or mold is fabricated using iron powder coated with plastic, the plastic should be removed and the iron powder should be sintered to be combined together. In addition, there is required post-processing, such as copper infiltration, to fill in gaps between among iron powder. However, the selective laser sintering has a shortcoming in that dimensional accuracy cannot be achieved because the material is contracted during the post-processing.
In the three-dimensional printing, a liquid bonding agent is selectively added to spread powder to form a product. Using such three-dimensional printing, a ceramic shell for investment casting can be made of ceramic powder, or a product can be made of powder including starch as a chief ingredient. However, the three-dimensional printing has a shortcoming in that contraction occurs due to thermal deformation because post-processing is required to increase the density and strength of a product.
In the laminated object manufacturing commercialized by Helisys Co., a product is fabricated by repeating a process of bonding together multiple pieces of paper in the form of thin films and cutting bonded papers using a laser beams. However, though the laminated object manufacturing has an advantage in that the manufacturing cost of a product is low because paper is used as raw material, it has a defect in that labor is required to remove a finished product from surrounding excess material after the fabrication of the product.
For example, in a case where a spherical product is fabricated, when the spherical product is fabricated by stacking and cutting multiple pieces of paper, labor is required to remove the finished spherical product from the remaining paper portion because the spherical product is surrounded by the remaining paper portion. Though plastic thin plate has been developed and can be utilized in fabricating a plastic product, there occurs also the same shortcoming as that with paper.
In accordance with fused deposition modeling commercialized by Stratasys Co., a product is fabricated in such a way that plastic material in the form of filaments is passed between heated nozzles each having a shape similar to an extrusion die and is bonded together while being melted. However, such fused deposition modeling has a shortcoming in that the surface of the product is rough because material in the form of filaments is employed.
Hereinafter, a rapid prototyping method for a product of functional material such as metal or a mold is described.
In laser engineered net shaping developed by Santia National Lab and recently commercialized by Optomec Co., a product is fabricated in such a way that metallic substrate is partially heated to form a melted pool and metallic powder is dropped into the melted pool using gas.
However, the laser engineered net shaping has a shortcoming in that dimensional accuracy of a product is deteriorated due to deformation during solidification because a product is fabricated of melted metal. Additionally, the laser engineering net shaping has a shortcoming in that a product having a protrusion or cantilever cannot be fabricated because a product is fabricated of melted material.
Shape deposition manufacturing developed by Stanford Univ. and Carnegie Mellon Univ. is a technique in which a metallic deposition is combined with CNC machining. In the shape deposition manufacturing, metal is deposited and machined to have a desired thickness and a boundary shape using a CNC milling, the remaining portion in the same plane is filled with another metal, and the material is CNC-machined to form a layer. After the layer is completed, shot peening is performed to eliminate residual stress. A desired product is completed through the above-described series of processes.
However, the shape deposition manufacturing has a shortcoming in that a long time is required to fabricate a product because a plurality of processes are performed to complete a product.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a rapid prototyping method and apparatus in which material, such as foamed resin, thermoplastic resin and thermosetting resin, in the form of a strip is cut and cut material pieces are bonded together and stacked using a four-degree-of-freedom linear heat-cutting device to have a desired width, inclinations and length in accordance with the computer aided design data of a product while the material is continuously supplied, thereby reducing a manufacturing time, improving the dimensional accuracy of manufactured products and decreasing the loss of material.
In order to accomplish the above object, the present invention provides a variable lamination manufacturing (VLM) process, comprising the steps of: coating strip-shaped material with a bonding agent while the strip-shaped material is conveyed; cutting the strip-shaped material being conveyed into material pieces of a variable width, variable inclinations and a variable length in accordance with the three-dimensional computer aided design data of a three-dimensional product using a linear heat source; stacking the cut material pieces on a moving table to be positioned in the corresponding positions of the three-dimensional product; and pushing the stacked cut material pieces to bond one piece to anther.
In accordance with a feature of the present invention, the method further comprises the step of cutting and storing the remaining material except for the cut material pieces.
In accordance with a feature of the present invention, the linear heat source is one of hot wire, laser, plasma, heat beam and heated gas.
In accordance with a feature of the present invention, the strip-shaped material is one of foamed resin, thermoplastic resin and thermosetting resin.
In addition, a variable lamination manufacturing (VLM) process, comprising: feed means for feeding a strip-shaped material; conveying means for horizontally conveying the strip-shaped material; coating means for coating the lower surface of the strip-shaped material with a bonding agent; cutting means for cutting the strip-shaped material being conveyed into material pieces in a variable width, inclinations and a length in accordance with the three-dimensional computer aided design data of a three-dimensional product using a linear heat source; holding and moving means for holding a cut piece and vertically moving the cut piece; and positioning means for three-dimensionally moving the cut material pieces so as to position the cut material pieces in place for a three-dimensional product.
In accordance with a feature of the present invention, the apparatus further comprises means for cutting and storing the remaining material except for the pieces used in fabricating the product.
In accordance with a feature of the present invention, the apparatus further comprises a paper feed roller, the paper feed roller supplies paper to the lower surface of the remaining material so as to prevent a bonding agent coated on the lower surface of the remaining material from being smeared on the conveying means when the remaining material passes through the conveying means.
In accordance with a feature of the present invention, the cutting means is a four-degree-of-freedom linear heat cutter that can perform translation and rotation.
In accordance with a feature of the present invention, the apparatus further comprises a pushing device, the pushing device pushing cut pieces stacked on the conveying means so as to bond one piece to another.